We propose to build the world's first combined x-ray computed tomography (XCT) and fluorescence tomography (FT) system. The construction of this system will create a new molecular imaging tool for researchers performing stem cell and cancer research. Stem cell research holds great promise for the development of cellular therapies for the treatment of disease and the development of cell tracking methods is therefore extremely significant. Several important scientific and technological innovations developed by our team of investigators at DxRay Inc. (Northridge, CA) and the University of California Irvine (UCI) allow the creation of a novel combined XCT and FT system. This project produces a unique dual-modality imaging methodology that combines functional and anatomical information and provides a new approach to molecular imaging. At the completion of the proposed project the combined XCT and FT system will add unique imaging capabilities to the animal imaging facilities at UCI. Furthermore, the innovative XCT technology developed by DxRay and the novel FT technology developed by UCI will be commercialized with support from Gamma Medica Ideas (Northridge, CA) who are very interested in this development and are providing a gantry for the combined system. Cellular therapeutics show great promise for the treatment of many diseases, but unfortunately few non-invasive techniques exist for tracking the cells after administration. The ability to non-invasively monitor cell trafficking in-vivo longitudinally is a pressing need for emerging cellular therapeutic strategies since this could be used to assess response. In-vivo tracking of cells has a broad range of potential applications in various diseases covering the fields of neurology, oncology, and cardiology. Therefore, to address the need for new multi-modality molecular imaging technologies, that are capable of the non-invasive in-vivo longitudinal imaging of mice for cell tracking, we propose to build the first of its kind combined XCT and FT system. The development of this very promising new technology, the first to combine FT with anatomical information from XCT in a relatively inexpensive and easy to use system, will create a powerful new tool for stem cell research and targeted drug delivery studies. We are developing novel in-vivo combined x-ray computed tomography (XCT) and fluorescence tomography (FT) system. This new technology will create a new type of dual-modality molecular imaging. This project will create new cell tracking capabilities and will benefit preclinical studies of cellular therapies.